How Luigi Mangione's notebook helped federal prosecutors build their case against accused CEO killer

It was writings laid bare in a notebook found in Luigi Mangione's possession, authorities say, that would help investigators build the federal case against him - a well-planned homicide that involved stalking the movements of his alleged victim, UnitedHealthcare CEO Brian Thompson.

An entry dated August 15, reads: "the details are finally coming together," according to a federal complaint unsealed Thursday. "I'm glad - in a way - that I've procrastinated," Mangione allegedly wrote, saying it gave him time to learn more about the company he was targeting, whose name was redacted by prosecutors.

"'The target is insurance' because 'it checks every box,'" the notebook read, according to the complaint.

The high-profile case took an unusual turn when Mangione, 26, was hit with new federal charges Thursday, on top of state charges he's already facing for the executive's December 4 killing in Manhattan, including for first-degree murder as an act of terrorism. The move appeared to take his lawyers by surprise.

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Now, the state and federal trials will "work in parallel," according to the Manhattan District Attorney's Office.

But Mangione's defense attorney Karen Friedman Agnifilo said the new charges - which include murder through use of a firearm, two stalking charges and a firearms offense - "raise serious constitutional and statutory double jeopardy concerns."

Though it's unusual for federal prosecutors to take on a case like Mangione's, legal experts say, a motion for double jeopardy - a doctrine that prohibits anyone from being prosecuted twice for the same offense - is unlikely to succeed.

Mangione, who will now be held in federal detention, is expected to face the state trial before his federal trial, prosecutors said. But with the federal charges now in play, it's unclear when Mangione will appear in state court. Federal prosecutors are next expected to seek an indictment from a grand jury.

The federal charges introduce the possibility of Mangione being sentenced to death if he's found guilty of the federal murder charge, while the state charges carry a maximum penalty of life in prison without the possibility of parole.

Prosecutors have not indicated whether they will seek the death penalty, and the decision would ultimately need to be approved by the US Attorney General.

Notebook helps feds build their case

The notebook authorities say was in Mangione's possession "contained several handwritten pages that express hostility toward the health insurance industry and wealthy executives in particular," according to the federal complaint.

In an entry on October 22, the writer called an upcoming investor conference "a true windfall" and described the intent to "wack" the CEO of an insurance company at the conference.

"The details from the notebook helped the feds build their case because it demonstrates the interstate stalking and the premeditated lying in wait," said David Shapiro, a lecturer at the John Jay College of Criminal Justice. "It's all there and part of a monthly long plan to cross state lines."

It's unusual for federal prosecutors to take on a case like Mangione's, Shaprio says, because historically, murder has been primarily prosecuted by the states since it's a crime committed in a specific jurisdiction.

The federal complaint added four new federal charges against Mangione, who was previously indicted on 11 counts this week in New York. The charges include two counts of second-degree murder, one of which alleges he committed murder "as a crime of terrorism."

But, bringing both state and federal charges is not unprecedented.

The push for federal charges came from the US Attorney's office, multiple law enforcement sources told CNN. Because the FBI was already involved in the investigation assisting the NYPD with out-of-town leads, FBI agents were asked to draw up the federal complaint based on evidence collected by NYPD detectives working on the state charges and police in Pennsylvania who arrested Mangione.

Federal prosecutors say they have jurisdiction in the case because Mangione's "travel in interstate commerce" - taking a bus from Atlanta to New York prior to the killing - as well as "use of interstate facilities" by allegedly utilizing a cell phone and the internet "to plan and carry out the stalking, shooting, and killing" of Thompson in broad daylight on a Manhattan sidewalk.

Defense questions concurrent charges

As Mangione made his first New York court appearance on Thursday, Agnifilo asked prosecutors to clarify whether there's a joint investigation among the federal and state prosecutors or two separate investigations.

Mangione's defense team appears to be poised to argue the concurrent charges may run afoul of his rights as a criminal defendant, several legal experts told CNN.

"The federal government's reported decision to pile on top of an already overcharged first-degree murder and state terror case is highly unusual and raises serious constitutional and statutory double jeopardy concerns," Agnifilo said. "We are ready to fight these charges in whatever court they are brought."

Agnifilo's request to prosecutors on Thursday is about "creating smoke and doubt," Shapiro said.

Mangione's lawyer could make a motion for double jeopardy, but it's unlikely to succeed, according to both Shapiro and Elie Honig, a CNN senior legal analyst and former federal and state prosecutor. The Supreme Court ruled in 2019 that state and federal agencies can bring charges against a person for the same conduct because they operate as separate entities.

"It does not violate double jeopardy principles to have the same person charged by the feds and the state separately," Honig told CNN. "The rationale there is, these are separate governmental entities, and in this case, the nature of the charges is different in technical respect."

It's not likely that a judge at the trial level "is going to take a chance on ruling this is double jeopardy and throwing it out," according to Shapiro, because "the societal stakes are huge."

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In court on Thursday, Mangione formally waived extradition and was flown from Pennsylvania to New York, arriving in Lower Manhattan surrounded by dozens of heavily armed law enforcement officers and the city's mayor.

Manhattan District Attorney Alvin Bragg said the state case against Mangione will "proceed in parallel" with the federal case.

According to Shaprio, however, "parallel" suggests "sort of two independent tracks, one above the other." Instead, he says, the two federal and state investigators are in fact "intersecting tracks, like threads in yarn. They are working together."

Finding an impartial jury could be tough

Federal prosecutors asked that Mangione be detained and his attorneys told the court they will not seek bail at the moment but reserve the right to do so later. Mangione will be held in Brooklyn's Metropolitan Detention Center, the only federal jail operating in New York City.

The biggest issue facing Mangione's prosecution is jury nullification because, according to Shapiro, "you're going to get a jury pool that is going to be somewhat familiar with the case."

The killing of Thompson, a husband and father of two, laid bare many Americans' fury toward the health care industry and Mangione garnered widespread support on social media after his arrest. Since his killing, officials have seen a "shocking and appalling celebration of cold-blooded murder," said NYPD Commissioner Jessica Tisch.

Jurors can choose to nullify the law and return a not guilty verdict based on their own personal convictions, Shapiro said, even when they believe evidence presented at trial proves guilt beyond a reasonable doubt.

"Jury nullification is the secret hope and dream of every defense attorney that doesn't have a case," Shapiro said. "You can't argue for nullification as a defense attorney. But a juror can decide on his or her own to nullify the law, to ignore the evidence, and to say they won't convict because of their own reasons."

What's at play in both the federal and state cases against Mangione, according to Shapiro, is that it's likely prosecutors don't want to try the case because it gives Mangione "a soap box to air his views."

"I think they want Mangione to plead out, which is why they're holding the death penalty against him," he said.

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